Direct Resonance Raman Evidence for a Trans Influence on the Ferryl Fragment in Models of Compound I Intermediates of Heme Enzymes

Czarnecki, Kazimierz; Nimri, Shay; Gross, Zeev; Proniewicz, Leonard M.; Kincaid, James R.

doi:10.1021/ja952177c

Cited by 103 publications

(101 citation statements)

References 56 publications

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“…The Fe-O bonding has been characterized by EXAFS and rR, which have shown the Fe-O bond distance to be approximately 1.6 Å with values of ν(Fe-O) in the range of 800-850 cm À1 [69,70]. These latter values are also sensitive to axial coordination as well as electron-withdrawing aryl substituents, which tend to result in negative shifts of ν(Fe-O) [63,[71][72][73][74].…”

Section: Fe(iv)-oxo Intermediatesmentioning

confidence: 99%

Transition Metal Complexes and the Activation of Dioxygen

Yee

Tolman

2014

Metal Ions in Life Sciences

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In order to address how diverse metalloprotein active sites, in particular those containing iron and copper, guide O₂binding and activation processes to perform diverse functions, studies of synthetic models of the active sites have been performed. These studies have led to deep, fundamental chemical insights into how O₂coordinates to mono- and multinuclear Fe and Cu centers and is reduced to superoxo, peroxo, hydroperoxo, and, after O-O bond scission, oxo species relevant to proposed intermediates in catalysis. Recent advances in understanding the various factors that influence the course of O₂activation by Fe and Cu complexes are surveyed, with an emphasis on evaluating the structure, bonding, and reactivity of intermediates involved. The discussion is guided by an overarching mechanistic paradigm, with differences in detail due to the involvement of disparate metal ions, nuclearities, geometries, and supporting ligands providing a rich tapestry of reaction pathways by which O₂is activated at Fe and Cu sites.

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Section: Fe(iv)-oxo Intermediatesmentioning

confidence: 99%

Transition Metal Complexes and the Activation of Dioxygen

Yee

Tolman

2014

Metal Ions in Life Sciences

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“…A different effect is evident in the doubly oxidized complex 4, which represents the most important intermediate in catalysis by heme enzymes (Compound I). [4] Possible interactions of the two unpaired electrons in the dp orbitals with the single porphyrin-based electron were classified as either: strongly ferromagnetic (e.g., in synthetic complexes with L = Cl À , ClO 4 À , MeOH), [5] exceedingly weak (e.g., in horseradish peroxidase, HRP, L = histidine) [6] and moderately strong antiferromagnetic (e.g., in chloroperoxidase, CPO, L = cysteinate).…”

Section: Introductionmentioning

confidence: 99%

The Electronic Structure of Iron Corroles: A Combined Experimental and Quantum Chemical Study

Tuttle

Bill

et al. 2008

Chemistry A European J

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There is a longstanding debate in the literature on the electronic structure of chloroiron corroles, especially for those containing the highly electron-withdrawing meso-tris(pentafluorophenyl)corrole (TPFC) ligand. Two alternative electronic structures were proposed for this and the related [FeCl(tdcc)] (TDCC=meso-tris(2,6-dichlorophenyl)corrole) complex, namely a high-valent ferryl species chelated by a trianionic corrolato ligand ([Fe(IV)(Cor)(3-)](+)) or an intermediate-spin (IS) ferric ion that is antiferromagnetically coupled to a dianionic pi-radical corrole ([Fe(III)(Cor)(.2-)](+)) yielding an overall triplet ground state. Two series of corrole-based iron complexes ([Fe(L)(Cor)], in which L=F, Cl, Br, I, and Cor=TPFC, TDCC) have been investigated by a combined experimental (Mössbauer spectroscopy) and computational (DFT) approach in order to differentiate between the two possible electronic-structure descriptions. The experimentally calibrated conclusions were reached by a detailed analysis of the Kohn-Sham solutions, which successfully reproduce the experimental structures and spectroscopic parameters: the electronic structures of [Fe(L)(Cor)] (L=F, Cl, Br, I, Cor=TPFC, TDCC) are best formulated as ([IS-Fe(III)(Cor)(.2-)](+)), similar to chloroiron corrole complexes containing electron-rich corrole ligands. The antiferromagnetic pathway is composed of singly occupied Fe d(z(2) ) and corrole a(2u)-like pi orbitals, with coupling constants that exceed those of analogous porphyrin systems by a factor of 2-3. In the corroles, the combination of lower symmetry, extra negative charge, and smaller cavity size (relative to the porphyrins) leads to exceptionally strong iron-corrole sigma bonds. Hence, the Fe d(x(2)-y(2) )-based molecular orbital is unavailable in the corrole complexes (contrary to the porphyrin case), and the local spin states are S(Fe)=3/2 in the corroles versus S(Fe)=5/2 in the porphyrins. The consequences of this qualitative difference are discussed for spin distributions and magnetic properties.

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“…It had therefore been puzzling that these results did not coincide with data for iron porphyrin p-cation radicals. These data showed the Fe IV =O frequencies to be quite insensitive to the porphyrin peripheral substituents [109,113,116], which were otherwise known to be able to modulate the radical symmetry state, as discussed in this review. Fe IV OTMTMP .…”

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confidence: 53%

Symmetry states of metalloporphyrin π-cation radicals, models for peroxidase compound I

Terner

Gold

Weiss

et al. 2001

J. Porphyrins Phthalocyanines

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Oxoferryl porphyrin p-cation radical active sites of compound I intermediates which are found in enzymes such as peroxidases and catalases have been extensively modeled by oxidized synthetic metalloporphyrins. The electronic symmetry states of these compounds were initially assigned on the basis of electronic absorption data. In recent years new experimental and theoretical results have become available which have led to a re-evaluation and modification of the original assignments. A historical perspective of these developments is provided in the context of recent NMR, resonance Raman, and other spectroscopic data and theoretical calculations for the synthetic models and enzymatic systems.

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Direct Resonance Raman Evidence for a Trans Influence on the Ferryl Fragment in Models of Compound I Intermediates of Heme Enzymes

Cited by 103 publications

References 56 publications

Transition Metal Complexes and the Activation of Dioxygen

Transition Metal Complexes and the Activation of Dioxygen

The Electronic Structure of Iron Corroles: A Combined Experimental and Quantum Chemical Study

Symmetry states of metalloporphyrin π-cation radicals, models for peroxidase compound I

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